Safety blasting device



, Feb. 27, 1962 f E. FlLsTRUP 'Y l '3,022,730

SAFETY BLASTING ,DEVICE FiledJuly 15, 195e A 2 sheets-sheet 2 INVENTOR. EDWARD C. FILSTRUP 'A 1ro/aus Vs States This invention relates to gas pressure devices, and more particularly to a novel self-contained and indestructible release mechanism for gas pressure device utilized in blasting operations.

Y In general the instant device is of that type provided with a chamber into which a gas, such as air, is introduced while the chamber is positioned in a mine bore juxtaposed to an under-cut formed in the coal or other ore to be mined. The sourceA of gas pressure, such as 4a gas pump, may be located remotely at a safe position spaced from the blasting chamber and is connected to the chamber by a suitable gas-conducting conduit, The chamber `has outlet ports which are controlled by a valve to close the chamber while gas is being introduced into the same.

'The valve is held in a close position by a member of a .strength which will permit it to withstand a predetermined pressure. When the gas pressure within the chamber builds up to a Value exceeding the pressure which the valve stop member will sustain, the member will cease to 'exert any restraining action thereby releasing the valve which moves in response to pressure acting thereon to a posit-ion at which the discharge outlets are opened. The opening action occurs in a very short interval of time so that there is a sudden release of the gas confined in the lchamber, which release is in a nature of a blast that is `elective to break down the coal, ore or other material the indestructible cartridges or shells with rupturable wall portions. Specifically, the rupturable wall portion takes vthe form of a disc which is associated with a discharge cap in such a manner that the central portion will be sheared from the remainder of the disc when a predetermined blasting pressure is obtained.

The only `disadvantage which results from the use of a rupturable disc -form of discharge control is that a new disc must be used with each new charge and the application of a new disc to a cartridge necessitates disassembly of the aforesaid discharge cap to permit the insertion of the new disc and the reassembling of the discharge cap to retain the disc in place. In addition, some provision must also be incorporated into the end cap to prevent the rupturable portion of the disc from being blown-out into the mine proper with possible injuries to personnel, or to become interminglmi with the ore for eventual separation. The development of an indestructible mechanism which would permit an accurate control of the discharge pressure of blasting charges would eliminate the cost of providing a new disc for each charge placed within the cartridge, the need for disturbing the cartridge assembly to effect substitution of a new disc, the danger of the .blown-out portion of the disc flying into the mine proper,

and a need for separation of the disc portion from the blasted ore.

arent @It means of connection, and involve possible premature tiring. Still another method for control of the release mechanisrn of the blast cartridges involve the use of multichamber blasting shells and an elaborate network of passageways and pistons to effectuate the release of -a valve like, whereinthe cartridge is operated by a novel selfcontained trigger mechanism.v

A further object of this invention is to provide a novel nondestructive trigger mechanism which is contained in a blasting cartridge, and which is actuated in response to a predetermined pressure. l

Other objects and advantages will become apparent from the following descriptions and drawings in which:

FIGURE 1 is a cross sectional view of a blasting cartridge head illustrating an embodiment of this invention.

FIGURE 2 is a cross sectional view of another blasting cartridge head illustrating an additonal embodiment of this invention.

FIGURE 3 is a cross sectional view of an/additional blasting cartridge head illustrating a still further embodiment of the invention.

FIGURE 4 is a cross sectional view of a modification of an embodiment illustrated in iFlG-URE 1, and

FIGURE 5 is Va cross sectional view of a blasting cartridge illustrating a further modication of the cartridges of this invention.

Referring to FIGURE l which illustrates one embodiment of the invention, the numeral 1 designates a tubular head for a blasting cartridge formed on any material'capatble of withstanding high gas pressures in the order of 15,000 to 20,000 pounds per square inch. The tubular head 1 is internally screw threaded at one end for screw threaded engagement at 2 with the casing 3 of a chamber of any conventional blasting cartridge, of which only a portion is shown. Typical of the charge chambers which casing 3 encloses is that disclosed in U.S. Patent No. 2,527,291. The head 1 bears against a shoulder 4 of the casing shown. The joint between the casing 3 and the head 1 is rendered leak proof by an -annular resilient sealing member S mounted in an annular groove 6 in casing 3. In forward spaced relations to the front edge of casing 3, the head 1 is preferably provided with a groove 8 which mounts an annular resilient sealing ring 7; The bore of the head 1 is preferably reduced slightly rear of groove 8 to define a narrow shoulder 9. In forward spaced relations to groove 8 the head 1 is provided with a plurality of radial discharge outlets 10 having their axis preferably inclined to both the head and the perpendicular to that axis.

The bore of head 1 is preferably again reduced slightly forward of the aforesaid outlets to provide a narrow shoulder 11. In forward spaced relations to shoulder 11 is a groove 12 which mounts an annular resilient sealing ring 13. The other end of the bore is enlarged to form a shoulder 14, and the extreme end portion of the bore is internally screw threaded for engagement with an end cap 15. 'Ille rear portion of end cap 15 contains a cylindrical bore 16 terminating in a base 17, the rear part of which contains a groove 17 which mounts an annular resilient sealing ring 18. The forward end of cap 1 5 contains 2 bores 19 and 20 in which extreme forward ends are internally screw threaded.

Mounted between head 1 and end cap 15 is an annular spaced ring 21 having a rearwardly extending annular lip 22 whose outside diameter is smaller than the inside diameter of head 1 to form an annular socket 23. Ring 21 has a forward extending tapered portion 24 which abuts the bore of end cap 15.

Slidably mounted within bore 19, of end cap 15, is a plunger 25, the rear portion of which is formed into an annular head 26 which abuts against a base 27 of bore 19. Extending rearwardly from head 26 into the chamber defined by bore 16 are a pair of dogs 28 pivotally connected at 29 to a lever 30. A resilient member 31, such as a helical spring, is slidably mounted about plunger 25, and is held in compression against head 26 by a plug 32 containing a cylindrical passageway 33 for slidable movement therein of plunger 25. Sealing members 34 and 35 seal the plug against the end cap 15 and the plunger 25, respectively. Head 26 contains a plurality of small passageways 36.

Slidably mounted in bore 20 is a pivot shaft 37 having a bifurcated end to serve as guides 38 for lever 30. A pivot shaft 37 is sealed against the end cap 15 by means of an annular resilient sealing means 63 which is mounted in an annular groove 64 formed about an intermediate portion of the body of shaft 37. Screwed into the forward end of bore 20 is an adjusting plug 39 slotted at 40.

A pivot link 41 is pivotally mounted through a square aperture 42 on a square bodied shaft 43. Shaft 43 may be mounted in any convenient manner, as in holes, in the walls of end cap 15, but preferably has one end accessible from the exterior of the end cap, which end may be slotted or chambered for reception of any convenient tool for turning of the shaft. Shaft 43 may be sealed to the cap by any convenient sealing means such as an O ring.

Pivot link 41 is restricted in its counterclockwise motion by a forwardly projecting point 44 which abuts lever 30, forcing the lever against shaft 37. In the embodiment shown the link defines roughly a right triangle with a square aperture 42 and point 44 located approximately at the base angles, with a pair of apertured dogs at 45 located roughly at the vertex angle.

A sleeve valve 46 is mounted snugly and slidably within the bore between shoulders 9 and 11. Extending forwardly from valve 46 is an annular skirt 47 having a diameter such that the skirt tits snugly and slidably in that portion of that bore, forward, to the right, of shoulder 11. As best illustrated at FIGURE 1, the skirt and valve are of a length to span the outlets 10 and also to span the groove 12. The annular resilient sealing member 13 serves as a seal to prevent leakage around the right hand end portion of skirt 47. Valve 46 is also provided with one or more openings 48 which communicate with both sides of the valve, and is also provided with a central opening 49. A valve terminal, comprising a pair of dogs 50 is mounted in opening 49 by means of stem 51, and secured thereto by a nut 52 screw threaded on the end of stem 51. A connecting link 53 is pivotally connected by means of pin 54 to dogs 50, and pivotally connected by pin 55 to the apertured dogs 45.

In operation as the pressure builds-up within the cartridge the passageways 48 in valve 46 and passageways 36 in head 26 of plunger 25 permit the force pressure to become equalized throughout the cartridge. As can be seen the plunger 25 is constructed so that the plunger 25 with head 26 offer a dierential area to the pressure within the cartridge. Accordingly, as the pressure buildsup within the cartridge, plunger 25 is urged `forward to the right against spring 31, in turn tending to pivotr 30 about fulcrum 39. As can be seen the resistance which spring 31 offers against plunger 25 can be controlled by proper adjustment of plug 32. Accordingly, by compressing spring 31 greater pressures in the cartridge proper will be required to move plunger 25.

For operation, pin 55 is on or below a line drawn from the center of pin 54 and shaft 43. The position of pin 55 is controlled by adjustment of shaft 37, which in turn controls the position of the lever 30. Positioning of shaft 37 toward the right in end cap 15 permits lever 30 to be urged also to the right, which in turn controls the position of pin 55 below the straight line connecting pins 43 and 54.

A follower sleeve 56 is positoned between the end of casing 3 and the end of sleeve valve 46. The follower sleeve 56 is of greater thickness at the end thereof facing the intake of the device than at its opposite end, and a shoulder 57 is formed in its outer periphery and is adapted to seat against the shoulder 9 to limit the travel of the follower. The sleeve 56 has a limited amount of free play or tolerance in its t within the head 1 for purposes to be described. It will be Vobserved that the annular resilient sealing ring 7 prevents the leakage of gas under pressure lengthwise of the follower sleeve at its outer surface. Consequently, the follower sleeve is subject to the application of a greater etective force to move it to the right than the force exerted to move the same to the left. At its right hand end the follower sleeve 56 is re duced in diameter externally to form a comparatively narrow annular point 58. The annular point has its edge lying in a plane transverse of the sleeve and the valve 46 against which it bears.

As will be observed the valve member 46 and ring 56 have a combined effective area, on the right side of the valve, for the application of a force less than the effective area on the left hand side of the valve. Consequently, this differential area urges the valve to the open position under the iniluence of the pressure in the cartridge.

In the operation the shell of FIGURE l is loaded manually by the insertion of an appropriate wrench inserted into a slot provided in key shaft 43 and turning of the shaft counterclockwise to the extent of its movement whereat point 44, of pivot link 41, urges lever 30 against shaft 37.

As noted above the triggering of the cartridge is coutrolled by adjusting the compression of spring 31 and by the positioning of shaft 37. For purpose of the illustration of the operation of this cartridge, as in actual use, spring 31 is compressed and shaft 37 is so positioned that the triggering action will be effective at a pressure of 7,5 00 pounds per square inch, and wherein pin 55 is below a straight line drawn between key shaft 43 and pin 54.

As pressure is introduced within the cartridge the effective force on the combined differential areas of valve 46 and of follower sleeve S6 urges the valve forward. The valve is arrested in its forward movement through connecting link 53 held against pin 55 and pivot link 41. Since pin 55 is below the axis of the cartridge, valve 46 will remain locked in position preventing any forward movement of the valve assembly. As suicient pressure builds up the plunger 25 moves to the right against the compression of spring 31. This movement of the plunger causes lever 30 to rotate about fulcrum 39 against point 44 of pivot link 41. Lever 30, in turn, is restraining the counterclockwise motion of link 41. When the blasting pressure builds up to the pressure desired the force acting on differential plunger 25 is suicient to overcome the restraining force exerted by pivot link 41. At the desired pressure, 7,500 pounds per square inch, the clockwise movement of lever 30 causes pivot link 41 to rotate in a clockwise motion to a point above the axis, defined by the straight line from key shaft 43 and pin 54, far enough to permit the forces in connecting link 53 ito be unrestrained. This permits valve 46 to move to the right, turning pivot link 41 and to open outlets 10 and head 1.

The movement of the valve tothe right, upon removal of all restraining or locking action is substantially instantaneous to open outlets 10 instantaneously whereat the gas of the charge is substantially instantaneously exhausted therethrough.

It will be noted that as a cartridge is being charged two opposed forces in the nature of the force moments come into play within the cartridge about shaft 43. During charging the force moment of connecting link 53 at pin 55 will be opposite and greater than the force moment exerted by lever 30 at point 44. As the pressure continues to build, the difference between the two force moments about shaft 43 decrease, is eliminated, and inally both are directed in the clockwise direction as the blasting pressure is reached. Immediately subsequent to the elimination of the difference in force moment pivot link 41 will be caused to turn clockwise on key shaft 43 triggering the discharge mechanism. As can be seen, as pin 55 continues to rise above the axis of the cartridge a continually greater lever, `or force, arm is provided for the forces in connecting link 53 to accelerate the forward motion of the valve mechanism. As can be observed,during the clockwise rotation of pivot link, a point will be reached at which the link is out of contact withlever 30. At this point, the force moment at point 44 is removed, with only the force 'moment at vpin 55'to` continue the rotation of link 41. The above described increasing lever, or force, arm at pin 55 permits the valve to snapopen for the substantially instantaneous opening of outlets'10 and discharge of the gas pressure contained in the gas cartridge.

The movement of the valve 46 during opening occurs very rapidly and some means of cushioning is necessary to prevent injurious impact.v Such impact is prevented by the construction of the annular ring 21 which entails the entry of the right end of skirt 47 into the annular socket, between the annular lip 22 of ring 21 and the bore of head 1, and the snug of said parts causes the building up of a high pressure within socket 23 in advance of skirt 47 adequate to prevent impact of the skirt against the ring 21.-

Although the pressures at which the cartridge discharges have been described as controlled by 'both spring 31 and the positioning of shaft 37, it can be readily seen that, within limits, the pressures may be controlled by the positioning of either thev spring or the fulcrum. Thus, pressures may be varied at a fixed setting of spring v31 by the simple positioningof shaft 37. Accordingly, at a new position setting of shaft v37, plunger 25 will be required to move a lesser or a greater degree to the right requiring a lower or agreater pressure respectively against the plunger, before triggering of the cartridge. I

A-t a fixed setting of spring 31 the position of shaft 37 permits the selection of the blasting pressureof which the cartridge is triggered. As noted above, with the posi'- tioning of shaft 37 forward -to .the right, lever 30 is also free to move to a more forward position in turn permitting pin 55 to be positioned a greater distance below the axis of the car-tridge. a This positioning of pin 55 below the -axis of the cartridge allow a greater lever, or force, arm for the forces in connecting link 53. With the greater lever arm available a greater force moment exerted by the valve 46 at pin 55 is present which has to be overcome by the differential pressure plunger 25. As can also be clearly seen, as the shaft 37 is moved sufficiently rearward to the left, a point may be reached for lever 30 to be positioned suiiiciently to the left to maintain pivot point S above the axis of the cartridge. When pivot point 55 is above the axis of the cartridge no locking or restraining action will be present to prevent the forward movement of valve 46,` and accordingly, valve 46 will be free to move forward to open outlets without any significant build-up of pressure within the cartridge. Conversely, as can be clearly seen, with a fixed setting of shaft 37, the pressure at which the cartridge will be triggered can be varied in response to the amount of compression adjusted in spring 31.

In the above described embodiment ofthe invention, the cartridge must be reloaded manually after each discharge. This embodiment of the invention insures against any dangerous build-up of gases within the cartridge during manual handling, transportation and positioning of the same within the ore.

However, if, in the above, a partial or manual reloading of the cartridge is desired, the modifications required, of the cartridge in FIGURE 1, for this purpose are illustrated in FIGURE 4. The cartridge is identical in all aspects to that of FIGURE 1 with the sole exception of the changes in the annular ring 21 and in the addition of a helical spring 121. An annular ring is substituted in the modification of FIGURE 4 for ring 21 of FIGURE 1. Ring 120, like ring 21, is mounted between head 1 and end cap 15 and has a rearwardly extending annular lip 122 whose outside diameter is smaller than the inside diameter of head 1 to form an annular socket 23. However, in place of the forward extending tapered portion 24 of ring 21, ring 120 is modified so that the inner wall of `annular lip 122 ex' tends rearwardly to a spring seating base, shoulder, 123". To provide. room for the movement of connecting link 53 ring 120 also'has av forward extending tapered portion 124. Tapered portion 124 may extend to the for'- ward face- 125 of vlip 122, or if desired, may abut the bore of end cap 15.

Mounted in compres'sion'agains't base 123 of ring 120 and between v alve 46'and aboutV connecting link 53 is a return spring 121 which eiects the closure by forcing valve 46 to move to the left afteriiring' of the cartridge, inthe manner described above' for the embodiment of FIGURE 1.- Either a partial closure or a complete closure, of discharge outlets 10 by valve 46, may be'obtained by an appropriate selection of spring 121. Partial closure may be accomplished by selection of a spring which is incapable of completely overcoming the friction exerted between the various moving parts, provided" said spring does not interfere with the functions' of the cartridge, above described and referenced to FIGURE l1 In like mannerpspring 121 may be selected to have strength sufficient to overcome all friction exerted between the moving parts to completely close discharge outlets 10 without interfering Awith the explosive functions and triggering mechanisms of the aforedescribed cartridge. if f The discharging functions of the modification of FIG- URE 4 is identical to'thatdescribed above, with "respect to the embodimentof FIGURE l, with 'anvadditional function of lreturning -valve 46 to a position of either partially closing or completely closing discharge outlets 10. The modification in5which dischargev outlets v1t) are partially closed by valve 446 is a preferred embodiment of the invention since it not only insures against the bui1d up of any dangerous pressures during handling prior to blasting, but in addition,i't presents a minimum of opening, in discharge outlets 10, through which coal, dust, water, and debris may enter the interior ofthe cartridge.

FIGURE 2 represents another embodiment of the invention wherein the reloading is automatically accoml plished after each discharge of the cartridge. After discharge of the cartridge, the triggering mechanism, hereinafter described, is'adapted to automatically' close the outlets in the cartridge head. The head assembly,ring Z1, valve 46 and connecting link 53 are identical to like components in FIGURE 1 and are identified by like reference numbers.

An end cap 60 is screw threadedly attached to the forward portion of head 1 in abutting relationship against head1 and against ring 21 and sealed thereto by means of an annular resilient sealing member 61 contained within groove 62. The forward portion of end cap 60 contains an internally screw threaded opening 63 having mounted therein a plug 64v and sealed thereto by means of a sealing member 65 contained in groove 66. An insert 67 is xedly mounted within end cap 60 and against the forward. end. Insert-67 contains an internally threaded bore 68 communicating with opening 63. Anexternally threaded cylindrical end plug 69 containing a depression, or dimple, 70 in its rear face and a slot 71 in its forward face, is threadedly mounted within bore 68 of insert 67. An adjustable screw assembly 72 comprising an internally threaded casing 73 and an externally threaded screw 74 is fixedly mounted on the inner wall of end cap 60.

A pivot link, or bell crank 79 is pivotally mounted within end cap 60 about a fixed pivot pin 75. Pivot link 79 contains in its rear portion a set of dogs 76 which are bored at 77. Link 79 extends downwardly into a lower sear portion 81, and the link is free to rotate in a counterclockwise motion until the sear porf tion 81 abuts against the adjustable screw 74. Adjustable screw 74 controls the extent of the counterclockwise motion of link 79. A connecting link 53 is pivotally connected to valve 46 by means of pin 82 and to dogs 76 by means of pin 83. A spring terminal 84 having an enlarged rear portion 8S is connected to pivot link 79 by means of pin 86 in a stud 88 extending rearwardly from enlarged head S8. v A second spring terminal 87 having an enlarged forward portion 89 is friction ally pivoted within dimple or depression 70 by means .of a rounded extension 90. Spring terminals 84 and 87 are held in spacial relationship to each other by means of` forward and, rear portions thereof, respectivelyhaving slidably mounted thereon the `resilientmember 91, which is held in compression thereon between enlarged portions 85 and 89.

Spring 91 urges the spring terminal 84, through the pin '86, to rotate pivot link 78 counterclockwise against adjustable screw 74, and to restrain valve 46 in close relationship to outlets 10. y

The magnitude of the effect of the force of spring 91 acting on pivot link 79 can be adjusted and controlled through adjustable screw 64 in plug 69. The position of the Sear portion of link 79, in a counterclockwise direction can be fixed by the forward or rear positioning of adjustable screw 74. The position of pivot link 79 in turn determines the position of pin 83 and 86 above a straight line connecting pins 82 and 75 hereinafter referred to as the. axis of the cartridge. The positioning of pins 83 and 86 above the axis of the cartridge in turn determines the'lever, or force, arms of the forces about pin 75 in the pivot link exerted by connecting link 53 and spring 91. The extent of compression of spring 91 between the enlarged portions 85 and 89 of spring terminals 84 and 87, respectively, is controlled by the forwardk or rear positioning of end plug 69. Slot 71 in end plug 69 provides a convenient means for theinsertion of an appropriate tool to rotate and thereby control the positioningy of the aforesaid end plug. The compression of spring 91 determines the magnitude of the effective force acting on pin 86 in pivot link 79.

In operation, as the pressure builds-up within the cartridge, the differential valve 46 is urged forward to the right but is, however, restrained in its forward motion by the pressure exerted on pressure link 79 by spring 91. At first, the force moment of the opposed forces acting on pins 83 and 86, determined by the distance of their lever, or force, arms from pivot pin 75, in link 79 resolved into the effective moment, by the summation of the individual moments, urges pivot link 79 to rotate counterclockwise against adjustable screw 74. As will be observed, with a continued build-up of pressure within the cartridge, valve 46, through connecting link 53, exents an -increasing force against pin 83, and accordingly increasing the force moment at this pin. When the force moment acquires a sufiicient value to :begin the rotation o-f pivot link 78 in a clockwise direction, it will be observed that the force arm at.pin 83 will increase whereas the force arm at pin 86 will decrease although in so doing it will compress spring 91 increasingthe force exerted on pin S6. It will be noted increasing the force moment at this pin.

thatv the increase in the force momentl at pin 83 is not only increased duey to the pressure build-up in the cartridge,k `but is also effected by Athe increase of the force arm at this pin which tends to accelerate the value of the force moment tending to rotate pivot link 79 in a clockwise direction. Ait the predetermined pressure, for example 8,000 pounds per squareA inch used in actual practice ofthe invention, determined by adjustment of screw 64 and insert 69, the value. of the force moment at pin 83, due to pressure in the chamber and increase of the -force arm, will have reached such a value as to overcome the opposed force moment at pin 86 to permit valve 46 to snap open with a substantially simultaneous discharge of the contained pressure through outlets 10.

After discharge of the cartridge 'the pressure is reduced to substantiallyV that of the surrounding atmosphere. This reduction ofthe contained pressure in turn substantially eliminates the force exerted by valve 46, through connecting link 53, on pin 83, whereby the value of the force moment is reduced to av value below the force moment exerted by spring 91 on pin 86. At this point, the force moment on pin 86 rotates pivot link 79 in the counterclockwise direction` against adjustable screw 74, in turn urging, through connecting link 53, valve 46 rearwardly to theleft to close outlets 10. This embodiment illustrates the invention Iwherein the blasting cartridge is automatically reloaded for successive firing.

FIGURE 3v illustrates a still further embodiment of the invention wherein the construction of head 1, valve 46 and connecting link is identical to that of the preceding embodiments and are identified by like reference numerals. An end cap- 95 containing a bore 96 has a reduced portion 97 of its outer diameter externally screw threaded for mounting within head 1. The open end of cap 95 abuts against ring @1, and is sealed to head 1 by abutment of the shoulder, formed by reduced portion 97, against the forward end of head 1, and by means of an annular resilient sealing member 61 contained within a groove 6-2.

Pivotally mountedy onl pin 98 is a pivot link 99 containing an internally screw threaded bore -100 in which is mounted an adjusting screw 101. Pivot pin 98 is fixedly mounted within end cap 95v in any convenient manner such as boring through thewalls of the end cap, insertion of pin and welding.

The counterclockwise rotation of pivot link 99 is restricted by fthe contact ofy adjusting screw 101 against a stopf102 Xedly mounted, within the end cap in any convenient manner such asin a case of pivot pin 98. The rear portion ofpivot link 99 is bifurcated into a pair of dogs 103 which are bored at 104. A connecting linkA 53v is pivotally connected rto valve 46 by means of valve pin 82l and to dogs 103 by means of pin 105 and bores 104. A -lower and forward portion of pivot link 99 is reduced toa lesser thickness and is bored for mounting of a pin 106. An arming and return spring 107 is pivotally connected in tension at one end to pin 106 and to the end cap in theforward portion thereof by means of pin 108.

In operation, as the pressure builds-up `within the cartridge, the differential valve 46 is urged forward to the right but is, however, restrained in its forward motion by the pressure exerted on link 99 yby spring 107. At lirst, the force moment of the opposed forces acting on pins 105 and 106, determined by the distance of their lever, or force, from pivot pin 98, in link 99 resolved into the effective moment, by the summation of the individual moments, urges pivot link 99 to rotate counterclockwise until its rotation is arrested by contact of adjustable screw i101 with stop 102. As will vbe observed, lwith a continued build-up of pressure within .the cartridge, valve 46, through connecting link 53 exents an increasing force against ypin 105 and accordingly When the force moment acquires a sui'icient value to begin the rotation of pivot link 99 in a clockwise direction, it will be observed that the force arm at pin 1-05 will increase whereas the force arm at pin'106 will also increase together with tensing of spring I107, thereby increasing the force exerted on p-in 106. It will `be noted that the. increase in the force moment atv pin 105 is not only increased to the pressure build-up in the cantridge lbut is also effected by the increase of force amt at this lpin which tends to accelerate the value of the force moment tending torotate pivot link 99 in a clockwise direction. An increase in the value of the force moment at pin 106 will also occur due to the increase of the force arm and the value of the force exerted by spring 107 at this pin. At a predetermined pressure, for example 8,000 pounds per square inch used in actual practice of the invention, determined -by adjustment of screw 101, the value of the force moment at pin 105, due to pressure in the chamber and increase of the force arm, will have reached such a value as to overcome the increased-value of the op- 'posed force moment at pin 106 to permit valve 46 to snap open with a substantially simultaneous discharge of the contained pressure throughout outlets 10.

After discharge of the cartridge the pressure is reduced to substantially that of the surrounding atmosphere. This reduction of the contained pressure in turn substantially eliminates the force exerted by valve 46, through connecting link 53, on pin 105, Iwhereby the value of the force moment is reduced to a value below the force moment exerted 'by spring 107 on pin 106. At this point, fthe force moment on pin 106 rotates pivot link 99 and adjusting screw 101 in a counterclockwise direction, until its motion is arrested by contact against stop 102. This motion of pivot link 9.9, in turn, urges through connecting link 53, valve 46 rearwardly to the left to close outlets 10. This embodiment again illustrates the invention -wherein the blasting cartridge is automatically reloaded for successive ring.

An illustration of still another embodiment of the invention is illustrated in FIGURE in which the embodiment of FIGURE 3 is utilized in the complete form described above with the sole modications provided in the closed end of cap 95 and arming and return spring 107. The end of cap is provided with an internally threaded bore 126 into which is screwed an externally threaded extension 127 of a spring housing 128. Housing 128 is provided with a bore 129 which is internally threaded at its forward portion 130 and terminating in its rear portion at a base 131. A plunger bore 132 eX- tends through extension 127 through base 13-1 to communicate with bore 129. A cup-shaped piston 133 is slidably mounted within bore 129 with 4its lip portion 134 disposed forward toward the open end of bore 129. A coiled arming spring 135 is mounted in piston 13-3 and is held in adjustable compression against a cupshaped depression 136 in the end of a housing plunger 137. The housing plunger 13-7 is screwedly mounted in the threaded portion 130 of housing 128.

Although not described in the embodiment of FIGURE 3, in view of its lack of function therein, pivot link 99 is provided with a sear portion 138 which abuts against a cylindrical plunger 139 having a rear reduced portion 140 slidably mounted through plunger bore 132 to abut against the rear face of piston 133. Annular resilient sealing means 141 may be inserted into radial grooves 142 provided in plunger bore 13-2. In like manner housing 128 may be sealed against the forward end of cap 15 by means of a circular sealing means 143 mounted into peripheral grooves 144 provided in the rear face of housing 128.

It is to be noted in the above that by reducing the rear portion 140, a differential pressure area is provided in plunger 139 rendering it responsive -to pressures within the cartridge.

After discharge of the cartridge to effectuate closure of discharge outletsl 1 0 a return `spring'145 is mounted in tension on pins 106 and 108.

' Another modilication may, -if desired, be provided;

er 139, wherein stop 102 will extend across the bore of end cap and will bepivotally mounted through or on the Wallsof the cap.

In operatioi1, pin will be positioned above'a line drawn from the axis of pin 98 and pin 82. As the pres-` sure builds-up within the cartridge, the differential valve 46 is urged forward to the right but, however, restrained in its forward motion by the abutment of sear 138 against plunger 139. Since plunger 139 has a differential areawhich is responsive to pressures within the cartridge, the plunger will be urged forward as the pressures buildup within the cartridge. The plunger, however, is restrained in its forward motion by abutment of rear portion 140 across the rear face of piston 133- which is urged rearward under the force of compression in spring i. With the continuation of pressure build-up within the cartridge, plunger 139 will gradually overcome the compressive force of spring 135 until the plunger withdraws from contact with sear 13-8. At this point the forward motion of differential valve 46 is unrestrained and the valve will snap open to instantaneously discharge the contained pressure through outlets 10.

It is to be noted that in the embodiment, FIGURE 5, the pressure at which the cartridge will discharge is controlled solely by adjustment of plunger 137 which determines the amount of compression imparted to spring 135. The sole function of adjusting screw 101, of this embodiment is to maintain the axis of pin 105 above a line drawn between the axis of pins 98 and 82.

After discharge of the cartridge the lpressure contained therein is reduced to substantially that of the surrounding atmosphere. Upon this reduction of pressure, spring 135, through piston 133 will push plunger 139 rearwardly against link 99, also return spring 135 will return pivot link 99 to the position in which valve 46 closes discharge outlets 10. It is immaterial whether pivot link 99 turns rst or subsequent to the return of plunger 139 against the link since in the design of pivot link 99 a ratchet action is obtained which permits the link to turn counterclockwise until adjustment screw 101 abuts against stop 102 at which position sear 138 locks against plunger 139. This embodiment against illustrates the invention wherein the blasting cartridge is automatically reloaded for successive tiring.

' Although the invention has been described with reference to specific embodiments and details, various modiiications will be apparent to one skilled in the art and are contemplated to be embraced within the invention.

t What is claimed is:

1. A blasting device comprising a cartridge body having discharge ports, a sleeve valve disposed in the body normally spanning and closing said ports to retain pressurized gas within said body, means for rapidly actuating said valve to open said ports comprising a pair of jointed links connected by a pivot pin, said links dening a connecting link joined to said valve and a pivot link pinned to the cartridge body by means of a shaft, the pivot points of said links being normally disposed in a substantially straight line relationship, a differential pressure plunger disposed within said blasting device, a lever within said device, said lever being connected at one end to the plunger, a pivot shaft disposed generally parallel to but spaced from said plunger providing a fulcrum for the lever, the opposite end of the lever making a driving connection with the pivot link, said plunger being operable to rotate said lever about the pivot shaft to drive the pivot link, and means including a spring operative to hold said plunger and said lever stationary in a position which retains said jointed links in said straight line link may be, rotated manually from the'open valve posi' tion to the closed valve position corresponding to said,

straight line relationship.

References Cited in the file of this patent UNITED STATES PATENTS Armstrong lan. Clench et al. Jan. Bugg Jan. Smithv Oct.

Filstrup: June 

